Turfgrass is widely used in landscaping, as a ground cover, and as a playing surface. For example, turfgrass is commonly found in parks, business landscaping, and suburban lawns. Examples of playing surfaces which utilize turfgrass include soccer and golf. This wide use of turfgrass is due in part to the many species of turfgrass and the concomitant variation in the characteristics and properties of the species.
It will be appreciated that the relative importance of any given property of turfgrass depends on both the species and application. Illustrative properties include the lushness or thickness, the texture, and the color of the grass. Of these properties, color is thought to be a particularly good indicator of the health of the turf. Accordingly, color is considered not only a key property--in and of itself as an aesthetic characteristic--but is also symptomatic of the overall health of the turfgrass. In view of this importance, the color of the grass is often closely monitored in many settings in which turfgrass is used.
Determining the color of turf to date has been a highly subjective exercise. The common method is for turf managers to use a scale of 1 to 9 with higher numbers corresponding to "greener" colors. Thus, in this system a poor yellow/brown color would be indicated with a "1" while an excellent dark green color would be indicated with a "9". While the system may qualitatively provide insight into the relative health of the grass, it has significant drawbacks. More specifically using this methodology, the "rated color" of the turf can vary depending on the health of the turf, the angle of the sun, the cloudiness, the presence or absence of dew, and the subjective perception of the viewer (e.g., what is "dark green" to one person may be "medium green" to another), among other factors. Additionally, color is generally recognized to have three major components: hue (red, yellow, green, blue, etc.); lightness (bright versus dark); and saturation (vivid versus dull). Given these three variables and the many terms used to express these variables, determining turf color is normally a highly subjective and inexact procedure.
Accordingly, there arises a need in the art to provide for an accurate apparatus and method which quantitatively measures turfgrass color on a consistent basis. Making such color measurements is known in other fields. One example is in paint mixing equipment. In that area, calorimetric techniques have previously been used to determine with some precision the hue, lightness and saturation of colors. Also, devices known as spectrophotometers have been constructed to measure color. A specific example of a spectrophotometer is manufactured by Minolta Company, Ltd., of Osaka Japan, under the model designation CM-525i series. The device uses a xenon arc lamp which is pulsed after a sample is located in a sample target area. The pulsed light enters an integrating sphere resulting in diffuse illumination of the test object. Light reflects off of the test object back into the integrating sphere. A converging lens gathers the reflected light onto a spectral sensor. The output from the spectral sensor is processed such that the device provides specific, reproducible color data in one of the several different spectral reflectance nomenclatures (e.g., XYZ or L*a*b*, among others).
Finally, quantitative analysis of turfgrass is not new. For example, The Toro Company (the assignee of the present invention), has used near infrared equipment to analyze turfgrass nutritional composition. After proper calibration, the results of such an analysis provide turf managers with information relating to levels of nitrogen, potassium, magnesium, iron, etc. in the turfgrass. In this manner, an indication of whether or not the plant is suffering from certain deficiencies can be ascertained.
Another system, distributed by Karsten, Inc., used a near infrared device in an effort to predict mineral content of grass by using one equation for all grasses. However, because all grasses (even within the same variety, but from different geographical areas) do not respond the same with different chemical/mineral levels (relative to the color of the grass with the differing levels), such system had significant drawbacks.
Therefore, there arises a need in the art for a method of and apparatus for quantitatively determining the color of turfgrass based on various ecotypes. Additionally, there arises a need in the art for a method and apparatus for determining nutritional health of turfgrass and predicting outcomes of changing nutritional parameters associated with quantitatively determining the color of the turfgrass. The present invention provides such a method and apparatus, while addressing the problems described above.